Treatment of a Field Case of Spirochaetosis with Tiamulin

Burch and his co-authors report the successful treatment of a field case in the UK of avian intestinal spirochaetosis caused by Brachyspira pilosicoli with tiamulin.

There has been much confusion over the significance of spirochaetes found in the caeca of laying hens and the impact they may have on egg production. In recent years, the situation has been made clearer and the presence of such species as Brachyspira pilosicoli have been shown to cause a mild, chronic disease in both layers and breeders and to reduce egg production by reportedly 5 per cent.

In the United Kingdom, a multi-age caged laying site with three separate flocks of approximately 12 000 birds each was chronically infected with B. pilosicoli but displayed few clinical signs except for a noticeable reduction in egg production and an increased mortality.

The flocks were treated for three days in the drinking water with tiamulin at 12.5 mg/kg bodyweight, and a steady improvement in performance was recorded.

The production results were compared with a flock that had been untreated with tiamulin previously, as a control, and one that had been treated at 25 and 45 weeks of age.

A 9.8 per cent improvement in egg production per hen housed up to 72 weeks of age and 9.7 per cent in total egg weight was recorded, as well as an 8.6 per cent reduction in actual hen mortality, in the tiamulin-treated flock in comparison with the untreated control.

After taking into account the difference in breeds used, there was only a 6 per cent reduction in egg production but an 8.84 per cent increase in mortality in the untreated flock compared with the individual breed's standard production data.

The cost of the disease was estimated at £14 million in the United Kingdom, based on a national laying flock of 30 million or 1.5 per cent of production.

Faecal examination for potentially pathogenic spirochaetes should be part of the differential diagnosis of under-performing laying flocks.